1. Field of the Invention
This invention relates to an improved process for the preparation of lactones and, more specifically, substituted furanones of the formula: ##STR2## wherein R and R.sub.1 are hydrogen or alkyl and R.sub.2 is a hydrocarbon radical or -O-hydrocarbon radical.
2. Description of the Prior Art
Johnson U.S. Pat. No. 2,433,827, describes the preparation of alpha-acetyl-gamma-butyrolactone [3-acetyldihydro-2(3H)-furanone] by reacting ethylene oxide with ethyl acetoacetate in an ethanol solution of an alkali metal hydroxide in which the temperature during the reaction is maintained between 0.degree. C. and -5.degree. C. for 48 hours and thereafter recovering the alpha-acetyl-gamma-butyrolactone by extraction and subsequent fractionation. The yield of the desired lactone is stated to be of the order of 60% but in actual practice has been found to be considerably lower. The Johnson process also suffers from the disadvantage of requiring operating temperatures of not higher than 0.degree. C. for a time period of at least 48 hours.
Noting the unduly prolonged reaction times required at temperatures below 0.degree. C., Lacey et al in Canadian Patent No. 546,573 disclose a process for the production of alpha-aceto-gamma-lactones by reacting an epoxide with an acetoacetate of a C.sub.4-6 tertiary alkanol at temperatures from -10.degree. C. up to +10.degree. C. Temperatures of 0.degree. C. to +3.degree. C are indicated to be preferred. Lacey et al further specify that the reaction is carried out by adding either a mixture of the reactants to aqueous alkali or by first forming the sodium derivative of the acetoacetate and adding the epoxide thereto.
It would be highly desirable if it were possible to carry out the reaction at even higher temperatures for shorter periods of time while at the same time significantly increasing the yield of the desired lactone product. These and other advantages are readily achieved by the improved process of the present invention.